1. Field of the Invention
The present invention relates to a battery charging controller and a portable electronic device which are configured to control battery charging in response to a charging-control signal sent from a CPU.
2. Description of the Related Art
A battery charging control LSI (a battery charging controller) has been known, which is configured to control battery charging in response to a charging-control signal sent from a central processing unit (CPU). By referring to FIGS. 1 and 2, an example of such a battery charging control LSI is described.
As shown in FIG. 1, a charging circuit 11 and a regulator 12 are provided to such a battery charging control LSI 4.
The charging circuit 11 is configured to be started upon detection of an insertion of an alternating current (AC) adapter (an application of an AC adapter voltage VAC), and then to send an adapter detection signal (an interrupt signal) for informing a CPU 1 of the detection of the insertion of the AC adapter.
Moreover, the charging circuit 11 is configured to switch on and off the AC adapter voltage VAC applied to a battery 2 by making an ON/OFF control of a pMOS transistor switch, in response to a charging-control signal sent from the CPU 1.
The regulator 12 is configured to be started upon detection of an insertion of the battery 2 (an application of a battery voltage VBAT), and then to start the CPU 1 by using an starting signal.
The CPU 1 is configured to be started upon detection of the starting signal sent from the regulator 12 (an application of a regulator voltage VREG).
Moreover, the CPU 1 is configured to be started upon detection of the above starting signal, and then to generate the above-described charging-control signal in response to the adapter detection signal sent from the charging circuit 11. Thereafter, the CPU 1 sends the thus generated signal to the charging circuit 11.
By referring to FIG. 2, descriptions will be provided for operations for controlling battery charging in a portable electronic device provided with a battery charging control LSI 4 as the one described above.
As shown in FIG. 2, when the regulator 12 detects the battery voltage VBAT in Step S201, i.e., when an insertion of the battery 2 is detected, the regulator 12 is started in Step S202.
In Step S203, the regulator 12 starts the CPU 1 by using an starting signal.
Thereafter, when the charging circuit 11 detects an application of the AC adaptor voltage VAC in Step S204, i.e., when the insertion of the AC adapter is detected, the charging circuit 11 is started, and then sends, as an interrupt signal, an adaptor detection signal to the CPU 1, for informing the CPU 1 of an insertion of the AC adaptor.
When the CPU 1 detects, in Step S205, the adapter detection signal sent from the charging circuit 11, the CPU 1 generates, in Step S206, the above-described charging-control signal in response to the adaptor detection signal, and then sends the thus generated signal to the charging circuit 11.
Thereafter, the charging circuit 11 controls the charging of the battery 2 by making an ON/OFF control on the pMOS transistor switch in response to the charging-control signal received from the CPU 1.
However, in a case of the conventional battery charging control LSI 4, even when power is off and the AC adaptor is not inserted, the regulator 12 constantly operates by using the battery voltage VBAT and the CPU 1 also operates by using the regulator voltage, after the battery 2 is inserted. This state of the battery 2 produces a problem that the increased power consumption of the battery 2 shortens the battery duration.